Date : 2009
Editeur / Publisher : [S.l.] : [s.n.] , 2009
Type : Livre / Book
Type : Thèse / ThesisLangue / Language : français / French
Résumé / Abstract : Le travail de cette thèse, en partenariat entre l'UPMC et CGGVeritas, consiste en l'étude de faisabilité théorique du suivi CSEM du déplacement latéral de l’interface huile/eau au sein d’un réservoir terrestre avec un dispositif permettant d'obtenir l'information sur la répartition des fluides sur une grande surface. Après un état des lieux des méthodes géophysiques appliquées au suivi de réservoir d'hydrocarbures, une présentation de la théorie sur les algorithmes de simulation est donnée (Méthode des Moments et différences finies). Le développement est plus approfondi pour la Méthode des Moments. Le dispositif qui a montré la meilleure sensibilité consiste en un dipôle source vertical enterré à mi-profondeur entre le réservoir et la surface, et des récepteurs horizontaux de champ électrique posés à la surface. Le niveau du signal 4D, i.e. la différence de champ mesuré à deux instants différents, reste légèrement au dessus du bruit ambiant que l'on peut éliminer par sommation. L’inversion 4D a montré la possibilité d'interpréter les données synthétiques CSEM en utilisant une seule position de source et une grille de récepteurs posés à la surface. Les images tirées de ces essais d'inversion font bien ressortir l'interface huile/eau. La non prise en compte d'une couche fine d'une dizaine de mètres, avec un fort contraste de résistivité par rapport à l'encaissant, est pratiquement sans effet sur le signal mesuré directement à la surface, mais réduit la résolution de la frontière huile-eau lors de l'inversion 4D. Une bonne connaissance de la distribution de conductivité électrique de l'ensemble du terrain environnant reste donc nécessaire à l'inversion de données CSEM 4D
Résumé / Abstract : Low frequency electromagnetic methods from a controlled source (CSEM : Controlled Cource ElectroMagnetic) have been applied for a little more than a decade in oil exploration. As a complement to seismic methods, they permit lowering of the risk of «dry holes», since they are more sensitive to the nature of the uid contained in rock. Because of the numerous successes encountered, and experience acquired, petroleum companies foresee extending application of CSEM to the monitoring of reservoirs under production. The principal problems are monitoring the oil-water interface to avoid loss of production due to invasion by water, and to estimate the e_ciency of improved techniques on the recovery rate for production (EOR : Enhanced Oil Recovery). The interface of oil and water is subject to an essentially lateral displacement due of low thickness of hydrocarbon reservoirs having an area that exceeds several square kilometres. The work of this thesis, done in partnership between UPMC and CGG Veritas, consists of the theoretical feasibility of monitoring CSEM for the lateral displacement of oil-water interface with a n apparatus that permits obtaining information on the distribution of uids for a large surface reservoir. We are particularly interested in the land milieu. After an examination of the status of applied geophysical methods on the monitoring for hydrocarbon reservoirs, a presentation of the theory of simulation algorithms is made. For this thesis, two codes have been developed, parallelized and used on parallel machines for which the calculation grid is European, EGEE. The _rst uses the semi-analytic Method of Moments for the frequency domain, and by extension, for the time domain. The second is based on _nite di_erence for the time domain. The development is more concentrated on the Method of Moments (code : EM MOM). The EM MOM code was able to be tested during a cooperative mission with CIPR (Center for Integrated Petroleum Research) at the University of Bergen, Norway. The code permitted doing a sensitivity analysis in the frequency domain to identify device geometries better adapted to the monitoring of a hydrocarbon reservoir (depth of 1000 meters). The apparatus that yields the greatest sensitivity consists of a vertical dipole source buried at mid depth between the top of the reservoir and the ground surface, and of horizontal receptors for electrical _eld set on the ground surface. The level of 4D signal, i.e., the di_erence of measured _eld at two di_erent instants («time lapse») remains at a level slightly over the ambient noise, which can largely be eliminated by summation (vertical stacking). A series of measures of ambient noise done by CGGVeritas, presented in the _rst part of this thesis, establishes this observation. A 4D inversion algorithm has demonstrated the possibility of interpreting the synthetic CSEM data by using a single position of source, and an array of receivers positioned on the surface. The images drawn from the inversion trials show the oil-water interface very well. The neglect of a narrow layer of a dozen meters having a strong contrast in conductivity with the terrain environment, is practically annulled for the signal measured at the surface, but reduces the resolution of the oil-water boundary in 4D inversion. A high level of knowledge of the distribution of electrical conductivity for the entire terrain environment is therefore necessary for the inversion of 4D CSEM data. iv